Vapor fixing unit for electrostatic printing



April 10, 1962 s. TEISER EI'AL 3,023,633

VAPOR FIXING UNIT FOR ELECTROSTATIC PRINTING 2 Sheets-Sheet 1 Filed March 24. 1958 iiik April 1962 s. TEISER ErAl. 3,028,683

VAPOR FIXING UNIT FOR ELECTROSTATIC PRINTING Filed March 24, 1958 2 Sheets-Sheet 2 United States Patent 3,028,683 VAPOR FIXING UNIT FOR ELECTROSTATIC PRINTING Sidney Teiser and Walter R. Sassaman, Rochester, N.Y.,

assignors, by mesne assignments, to Magnefax Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 24, 1958, Ser. No. 723,418 3 Claims. (Cl. 34-151) The present invention relates to electrostatic printing and, more particularly, to a separate fixer unit for fixing or fusing developer material applied to a surface bearing an electrostatic image.

An object of the present invention is to provide a new and improved fixing apparatus for use in electrostatic printing.

Another object of this invention is to provide a new and improved separate fixing apparatus for fixing developer material applied to a surface bearing an electrostatic image, the apparatus being designed to be used by a person relatively unskilled in the art and technique of electrostatic printing.

Yet another object of this invention is the provision of a new and improved fixing apparatus for fixing developer material adhering to a single sheet of paper or the like bearing a photoconductive layer treated so as to have an electrostatic image of printed material to be copied.

A further object is to provide a new and improved fixing apparatus for use in electrostatic printing, the apparatus being simple to operate and inexpensive to manufacture and maintain. A still further object is to provide a new and improved fixing apparatus for use in electrostatic printing for quickly and conveniently fixing one or more sheets each bearing an image of a copied item, the apparatus being designed to accept one sheet at a time and to fix the developer material applied to the sheet within a short time. I I

These and other desirable objects may be attained in the manner disclosed as an illustrative embodiment of the invention in the following description and in the accompanying drawings forming a part hereof, in which:

FIG. 1 is a perspective view of the fixing unit according to the present invention;

FIG. 2 isanother perspective view of the fixing unit showing the sheet holding tray receive a sheet to be fixed;

FIG. 3 is an enlarged section taken approximately on the line 33 of FIG. 1 to show the seal at the front to prevent evaporation of the chemical fixer;

FIG. 4 is a plan view of the tray for holding the sheet, a portion of th cover member being broken away to show the bottom sheet receiving member;

FIG. 5 is a plan view of the chemical tray withdrawn from the other components of the unit; and

FIG. 6 is an enlarged section taken approximately on the line 6--6 of FIG. 2 and showing the side runners for the sheet receiving tray.

The same reference numerals throughout the several views indicate the same parts.

In electrostatic photocopying or printing, briefly reviewing its principles, an insulating surface such as a sheet of paper or the like is provided with a coating or surface layer of a suitable photoconductive material. The surface layer is given an electrostatic charge and is then exposed to light rays either reflected from or transmitted through a sample or original to be copied. The light rays dissipate the electrostatic charge in certain areas of the sheet, thus forming a latent image of the sample in other areas of the sheet where the electrostatic charge is retained. The sheet bearing the latent image is then subjected to the action of a developer apwithdrawn and opened to paratus where a developer material containing a dye is applied to the image areas. At this point the developer material adheres to the charged image areas by means of electrostatic attraction, and thus makes the latent image visible. The sheet is then passed to a fixing unit wherein the dye is adhered permanently to the sheet so as to not rub off under normal usage.

The present invention is concerned with the fixing apparatus and is particularly designed for an electrostatic printing process carried out by someone relatively unskilled in the art and technique of electrostatic printing in general. It is desirably used, for instance, by an office having an electrostatic copying unit. The fixing unit herein described is a separate unit suitable for fixing a single page at a time and, as will be apparent, is relatively simple to operate, easily maintained, and inexpensive to manufacture.

The fixing or fusing unit according to the present invention, as illustrated generally in FIG. 1, employs a chemical fixing agent or vapor fixer. With this type of fix, fumes are given off within a substantially closed housing and react with the developer mix material, more specifically with the dye contained in the developer, so that the dye adheres permanently to the sheet. To this end, a rectangular housing is provided comprising a top wall 11, a bottom wall 13, a pair of side walls 15 and 17, and a rear wall 19. One or more walls of the housing may be provided by a cabinet containing other units of the electrostatic copying apparatus. The housing is open at one end for receiving a lower or chemical tray 21 and an upper or sheet receiving tray 23. The upper tray 23, of course, is removable to receive the sheet to be fixed, and, as will be explained in greater detail hereafter, the chemical tray 21 is also removable to allow replenishing of the chemical.

The sheet receiving tray 23, referring to FIGS. 2 to 4, comprises a bottom member 25 having a rectangular opening in which a screen 27 is supported. A cover member 29 is hinged to the bottom member 25 by hinges 30 at a point beyond the inner end or" th rectangular opening. The bottom member 25 is desirably provided with a forwardly projecting tab 31 at its front edge to facilitate pushing the tray 23 into the housing and removing it from the housing. At the rear end, the bottom member 25 may be notched out to form a rectangular recess 33 between the side rails. The side rails thus project rearwardly a substantial distance beyond the hinge axis of the hinges 30 so that the sheet receiving tray 23 may remain partly within the housing while placing a sheet on the tray or removing it from the tray, as will be clearer from the discussion to follow.

The members 25 and 29, and also the housing, are preferably made of sheet metal, and should be of material which is not affected by the chemical agent applied.

,- The screen 27 is sandwiched at its four edges between overlapping portions of the bottom member 25 as shown in FIG. 3. When in use, a sheet 35 to be developed rests on the screen 27 face down, it being understood that the developing material adhering to the latent electrostatic image surface of the sheet faces the chemical tray below. The corners of the screen 27 are preferably cut out to provide an open space 37 at each corner to allow finger room to enable the sheet 35 to be readily picked up ofi of the screen 27. The screen 27, of course, is made of a suitable wire or plastic material which does not react with the chemical fixing agent or with the developing material carried by the bottom surface of the sheet 35. The cover 29 is conveniently provided with a forwardly projecting tab 39 so that the cover may conveniently be raised off of the bottom member 25 when a sheet 35 is being inserted into or removed from the tray 23. The cover is also desirably provided with a rectangular recess Patented Apr. 10, 1962 3 41 at its forward edge laterally alined with the tab 31 carried by the bottom member 25 to provide a finger recess when pulling out the tray.

The lower or chemical tray 21 includes a flat bottom plate 43 which is bent downwardly and rearwardly at its forward edge to provide a laterally extending clip 45 which hooks over the forward edge of the bottom wall 13 of the housing. Secured to the forward part of the plate 43 is a laterally extending block 47. The block 47, as is evident from FIG. 3, extends upwardly toward the upper tray 23 when the unit is assembled and cooperates with a downwardly extending ridge 49 on a bumper secured to the under side of the forward edge of the bottom member 25. With the exception of when the tray 23 is withdrawn for inserting or removing the sheet 35 to be fixed, the cover 29 of the upper tray 23 abuts the top wall 11 of the housing and the ridge 49 is in engagement with the block 47 for substantially the entire width of the housing, thereby providing a reasonably tight closure for the front of the housing to prevent the chemical fixing agent vapor from escaping into the surrounding air.

As best seen in PEG. 5, the forward edge of the block 47 and the sheet 43 are substantially the same width as that of the housing. The rear edge of the block 47 and the remainder of the bottom sheet 43 are narrowed in width to allow room at either side for a runner or rail for supporting the top tray 23, as best seen in FIG. 6. Each of the side runners or rails includes a horizontal track 53 in abutment with its respective side wall 15 or 17, a substantially vertical supporting wall 55 and an inwardly bent securing flange 57, the flange 57 being fastened to the housing bottom wall 13 in any convenient manner, as by welding or riveting. The side runners are preferably bent from a single strip of sheet metal and may, if desired, be fixed to one of the side walls in addition to the bottom wall. Inasmuch as the upper sheet receiving tray 23 is substantially the same width as the clear space within the housing, it can be seen that the tray 23 may he slid on the track members 53 until its rear edge abuts the rear wall 19 of the housing.

Secured to the upper surface of the bottom plate 43 of the chemical tray 21 just rearwardly of the block 47 is an absorbent pad 61. The pad 61 may suitably be of felt or absorbent paper or the like. The pad is moistened with the chemical fixing agent and underlies the screen 27 so that its fumes rise to come into contact with the bottom surface of a sheet 35 to be fixed. Any appropriate chemical fixing agent may be used, such as for example, tetraethyl chloride.

The tray 21 is preferably removable so that the chemical applied to the pad 61 may be renewed. As can be seen in FIG. 1, a downwardly projecting tab 63 is fixed to the front edge of the bottom plate 43 to be grasped by the fingers to pull the tray 2i forward.

To summarize the operation of the fixing unit, the unit is normally assembled as in FIG. 1 with both the trays 21 and 23 inserted within the housing and extending horizontally. The open end of the housing is substantially closed by the abutment of the forward edge of the tray 23 with the block 47 on the bottom and with the top wall of the housing 11 on the top. Vapor from the chemical fixing agent with which the absorbent pad 61 is saturated fills the open areas within the housing but is substantially retained within the housing. When it is desired to fix a sheet 35 bearing an electrostatic image to which adheres a suitable developing material, the tray 23 is pulled forwardly on the tracks 53 by grasping the projecting bottom member tab 31. The tray 23 may be pulled completely out of the housing or, preferably, as shown in FIG. 2, until the hinges 30 are just out of the housing. The side rails of the tray structure still project far enough into the housing to support the tray structure in cantilever fashion even when the hinges 30 are outside of the housing. The cover 29 can be raised by lifting upwardly on the tab 39, and a sheet 35 to be fixed is then placed face down on the screen 27, the cover 29 is lowered, and the tray is pushed backward into the housing.

The developing material on the sheet 35 will immediately come into contact with the vapor arising from the chemical fixing agent carried by the absorbent pad 61. After a short time, about ten seconds, the tray 23 is again pulled forwardly and the cover 29 raised so that the sheet 35, now fixed, may be removed from the fixing unit. The tray 23 is then returned to its position within the housmg.

The chemical fixing agent carried by the absorbent pad 61 may be renewed from time to time as required. To accomplish this, the upper tray is first removed, and then the lower or chemical tray 21 is pulled out by grasping the tab 63 projecting downwardly from the forward edge of the bottom plate 43. After suitably saturating the pad 1, the tray 21 is simply slid back into place. The resilient spring clip 45 on the chemical tray 21 grips the edge of the stationary housing sufficiently tightly to prevent the chemical tray from being withdrawn accidentally when the paper carrier tray 23 is pulled forwardly. Of course it is easy to pull on the tab 63 with suflicient force to overcome the resistance of the spring clip 45, whenever it is purposely desired to withdraw the chemical tray 2i in order to replenish the chemical.

It can be seen that the fixing unit according to the present invention may be operated by any one, such as ordinary office help, who are relatively unskilled in the art and technique of electrostatic printing. A bottle of the chemical fixing agent is ordinarily supplied with the fixing unit, and it is obvious to anyone operating the device when the chemical on the pad 61 need be replenished. The fixing unit is conveniently made mainly of sheet metal and may be inexpensively manufactured in view of its relative simplicity. Because of the relatively short amount of time needed for the vapor fix to operate, a succession of sheets 35 may be fixed within a reasonable amount of time.

It is seen from the foregoing disclosure that the above mentioned objects of the invention are well fulfilled. It is to be understood that the foregoing disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

What is claimed is:

1. A fixing apparatus for use in electrostatic printing comprising a substantially air tight rectangular housing open at one end, a lower tray rcmovably received within said housing and having an absorbent pad saturated with a vapor fixer, a pair of tracks mounted at either side of said housing, an upper tray slidably received within said housing on said tracks, said upper tray including a bottom member having an opening, a screen supported within said opening for receiving a sheet to be fixed, and a cover hinged to said bottom member and overlying said screen, said trays and housing cooperating at their forward edges to substantially seal said open end of said housing.

2. A fixing unit for use in electrostatic printing comprising a substantially air tight rectangular housing open at one end, a substantially horizontal lower tray removably received within said housing and having an absorbent pad saturated with a vapor fixer, track means within said housing, a substantially horizontal upper tray slidably received on said track means and including a bottom member having an opening, a screen supported within said opening for receiving a sheet to be fixed, and a cover hinged to said bottom member and overlying said screen, said trays having engaging abutment means at their forward edges cooperating with said housing to substantially seal said open end of said housing.

3. A fixing apparatus for use in electrostatic printing comprising a substantially air tight rectangular housing open at one end, a lower tray removably received within said housing and having an absorbent pad saturated with a vapor fixer, clip means for normally retaining said lower tray Within said housing, track means at either side of said housing, an upper tray slidably received Within said housing on said track means and having an opening, a screening supported Within said opening for receiving a sheet to be fixed, said sheet being placed face down on said screening With its developed image toward the lower tray to be exposed to the vapor fixer fumes rising therefrom, and abutment means on the forward ends of said trays in engagement With each other and cooperating with the engagement of said upper tray with the upper Wall of said housing for substantially sealing the open end of said housing, said upper tray being pulled forwardly to project from the housing in cantilever fashion to replace the sheet being fixed at the end of each fixing operation While the lower tray is removed normally only to replenish the vapor fixer.

References Cited in the file of this patent UNITED STATES PATENTS 303,069 Swift Aug. 5, 1884 366,421 Mendenhall July 12, 1887 557,043 Adams Mar. 23, 1896 950,689 Deming Mar. 1, 1910 1,082,399 Brenauer Dec. 23, 1913 1,203,646 Oliver Nov. 7, 1916 1,954,577 Reddin Apr. 10, 1934 2,214,425 McNamara Sept. 10, 1940 2,684,301 Mayo July 20, 1954 2,776,907 Carlson Ian. 8, 1957 

